diff --git a/README.md b/README.md
index ef1f8e2..1078b98 100644
--- a/README.md
+++ b/README.md
@@ -244,6 +244,10 @@ globalAgent=npm
 
 # custom configuration file path
 export NI_CONFIG_FILE="$HOME/.config/ni/nirc"
+
+# environment variables have higher priority than config file if presented
+export NI_DEFAULT_AGENT="npm" # default "prompt"
+export NI_GLOBAL_AGENT="npm"
 ```
 
 ```ps
diff --git a/src/config.ts b/src/config.ts
index fdcc06a..22f59cb 100644
--- a/src/config.ts
+++ b/src/config.ts
@@ -36,6 +36,13 @@ export async function getConfig(): Promise<Config> {
         ? ini.parse(fs.readFileSync(rcPath, 'utf-8'))
         : null,
     )
+
+    if (process.env.NI_DEFAULT_AGENT)
+      config.defaultAgent = process.env.NI_DEFAULT_AGENT as Agent
+
+    if (process.env.NI_GLOBAL_AGENT)
+      config.globalAgent = process.env.NI_GLOBAL_AGENT as Agent
+
     const agent = await detect({ programmatic: true })
     if (agent)
       config.defaultAgent = agent
diff --git a/test/config/.nirc b/test/config/.nirc
new file mode 100644
index 0000000..1edd853
--- /dev/null
+++ b/test/config/.nirc
@@ -0,0 +1,2 @@
+defaultAgent=npm
+globalAgent=pnpm
\ No newline at end of file
diff --git a/test/config/config.test.ts b/test/config/config.test.ts
new file mode 100644
index 0000000..71a7373
--- /dev/null
+++ b/test/config/config.test.ts
@@ -0,0 +1,49 @@
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { beforeEach, expect, it, vi } from 'vitest'
+
+const __dirname = dirname(fileURLToPath(import.meta.url))
+
+beforeEach(() => {
+  vi.unstubAllEnvs()
+  vi.resetModules()
+})
+
+vi.mock('find-up', () => ({
+  findUp: vi.fn(),
+}))
+
+it('has correct defaults', async () => {
+  const { getConfig } = await import('../../src/config')
+  const config = await getConfig()
+
+  expect(config).toEqual({
+    defaultAgent: 'prompt',
+    globalAgent: 'npm',
+  })
+})
+
+it('loads .nirc', async () => {
+  vi.stubEnv('NI_CONFIG_FILE', join(__dirname, './.nirc'))
+
+  const { getConfig } = await import('../../src/config')
+  const config = await getConfig()
+
+  expect(config).toEqual({
+    defaultAgent: 'npm',
+    globalAgent: 'pnpm',
+  })
+})
+
+it('reads environment variable config', async () => {
+  vi.stubEnv('NI_DEFAULT_AGENT', 'npm')
+  vi.stubEnv('NI_GLOBAL_AGENT', 'pnpm')
+
+  const { getConfig } = await import('../../src/config')
+  const config = await getConfig()
+
+  expect(config).toEqual({
+    defaultAgent: 'npm',
+    globalAgent: 'pnpm',
+  })
+})